Detection of the singularities of a complex function by numerical approximations of its Laurent coefficients
- 73 Downloads
For several applications, it is important to know the location of the singularities of a complex function: just for example, the rightmost singularity of a Laplace Transform is related to the exponential order of its inverse function. We discuss a numerical method to approximate, within an input accuracy tolerance, a finite sequence of Laurent coefficients of a function by means of the Discrete Fourier Transform (DFT) of its samples along an input circle. The circle may also enclose some singularities, since the method works with the Laurent expansion. The DFT is computed by the FFT algorithm so that, from a computational point of view, the efficiency is guaranteed. The function samples may be obtained by solving a numerical problem such as, for example, a differential problem. We derive, as consequences of the method, some new outcomes able to detect those singularities which are close to the circle and to discover if the singularities are all external or internal to the circle so that the Laurent expansion reduces to its regular or singular part, respectively. Other singularities may be located by means of a repeated application of the method, as well as an analytic continuation. Some examples and results, obtained by a first implementation, are reported.
KeywordsNumerical algorithm Software suite Interactive software Complex singularities Laurent coefficients Analytic continuation
Unable to display preview. Download preview PDF.
- 3.Finkston, B.: Cluster data by using the mean shift algorithm. https://it.mathworks.com/matlabcentral/fileexchange/10161-mean-shift-clustering
- 15.Needham, T.: Visual complex analysis. Clarendon Press, Oxford (1999)Google Scholar
- 16.Rizzardi, M.: LaurentCoeffs. http://dist.uniparthenope.it/mariarosaria.rizzardi (2017)
- 19.Weeks, T.: Numerical inversion of laplace transform using laguerre functions. J. ACM, 13 (1966)Google Scholar
- 20.Wegert, E.: Visual complex functions: an introduction with phase portraits. Birkhäuser/Springer (2012)Google Scholar
- 21.Wegert, E.: Phase plots of complex functions, http://it.mathworks.com/matlabcentral/fileexchange/44375-phase-plots-of-complex-functions. (upyeard 2014) (2013)
- 22.Wegert, E.: Complex function explorer. http://it.mathworks.com/matlabcentral/fileexchange/45464-complex-function-explorer (2014)